US2076991A - Method of attaining improved felting of the fibers in paper pulp on the wet part of paper and board making machines - Google Patents

Description

P 13, 1937- s. P. H. E. HOLGERSSON ET AL 2,076,991 METHOD OF ATTAINING' IMPROVED FELTING' OF THE FIBERS IN PAPER PULP 0 THE WET, PART OF PAPER AND BOARD MAKING MACHINES Filed April 4, 1935 2 Sheets-Sheet 1 P" 1937. s. P. H.' E. HOLGERSSON ET AL 2,076,991

METHOD OF ATTAINING IMPROVED FELTING OF THE FIBERS IN PAPER PULP ON THE WET PART OF PAPER AND BOARD MAKING MACHINES Filed April 4, 1955 2 Sheets-Sheet 2 Patented Apr. 13, 1937 PATENT OFFICE METHOD OF ATTAINING IMPROVED FELT- ING OF vTHE FIBERS IN PAPER PULP ON THE WET PART OF PAPER AND BOARD MAKING MACHINES Sigbjiirn Paul Herbert Storvik, and William Molndal, Sweden Ebbinghaus Holgersson, Anders. Eugen Tibell,

Application April 4, 1935, Serial No. 14,718

1 In Sweden April 7,1934

2 Claims.

A number of inventions have already been made with the object of achieving better'felting of the pulp fibers at the wet-end of paper-making machines. Most of the devices used consist in mem- 5 bers which are caused to vibrate, thus producing an agitation of the pulp-fiber suspension. However, in all the devices hitherto employed, the vibrating members are of such a construction and size that they permit of only comparatively slow movements and for this reason only relatively unsatisfactory results have been attained in most cases. The reason for this may be plainly seen if we observe what happens at the wet-end .of a Fourdrinier machine which is fitted with a vibrating breast roll or with the entire wire-part vibrating. If we imagine that a drawing pen were fixed to the stufi-box on the apron so that it would draw a line on the moving wire-cloth, aperiodic curve would be drawn on the latter with, on account of the relatively slow vibration,

a long'wave-length and very small maximum.

angles towards the machine-direction. The

curve thus obtained shows on the whole the direction in which most of the pulp-fibers are pointing during the felting, since it is a fact that the fibers tend to arrange themselves in a direction parallel to the momentary relative motion between the flowing, undrained pulp-suspension and the wire, i. e., in the directions which are indicated for each instant by the above-mentioned, imagined curve. This circumstance is, of course, rather obvious, since as soon as any point on a fiber floating in the pulp-suspension touches either the wire or pulp which is lying on the wire and already drained and felted, the point. in question must receive acomponent of motion from the wire, while the rest of the fiber is under the direct influence of the surrounding pulp and water suspension.

When the motions of the wire and of the fibersuspension do not coincide from the beginning, and the above-mentioned point of contact between the fiber and the wire or between the fiber and pulp already felted on the wire does not 4 coincide with the centre of the fiber, the result must be that the fiber looses its equilibrium and is turned Ina direction more or less parallel to the above-mentioned relative motion. Thatthis is actually true can be proved in several ways.

For example, it is shown by microscopical examinations of paper as well as by pure tests of strength that most of the fibers in machine-made paper lie approximately in the manner indicated .by the abovementioned relative curve. Thus, if this curve, as it has hitherto been, is very vflat,

it is evident that the strength of the paper in the cross direction must at all points be considerably lower than the strength in the longitudinal direction of the paper.

The characteristic feature of the present invention is that the above-mentioned relativecurve.

is caused to be of very short wave-length. This is achieved by producing either in the wire itself or in the flowing fiber-suspension high-frequency vibrations (at least 1000-6000 vibrations per minute) at a right-angle to the machine-direction. On normal paper-machines of for instance the Fourdrinier type,.a relative curve is obtained between the undrained pulp and the wire with a wave-length approximately equal to the length of the fibers. Thus, paper made according to this invention is characterized by the fact that the fibers do not lie-according to afixed mean-curve, more or less fiat in appearance, but the entire felting-construction in such paper will be more or less independent of the machine-direction.

In this connection it should be mentioned that the vibrations are intended to produce a rapid relative movement between the flowing, unfelted fiber-suspension and the wire or the layer of already felted and partly drained pulp lying on the wire. When, for example, the wire vibrates, the object aimed at is not to cause agitation of the fiber-suspension but tb produce the abovementioned relative motion. Obviously, it will be advantageous when the wire vibrations cause the flowing suspension to vibrate also, but, in that case, the oscillations of the wire and those of the suspension must always be in opposite directions.

The inventors are of the opinion that the felting or weaving together of the fibers is mainly affected by the conditions on and close to the line where the pulp-suspension meets the moving wire. With reference to this, the invention is illustrated in the forms of construction shown schematically by the accompanying drawings. Fig. 1 is a plan view and Fig. 2 a vertical section of the wire-part of an ordinary Fourdrinier machine up to the apron. Fig. 3 is a longitudinal section of the portion of the wire-part close to the stufi-box. Fig. 4 shows a form of construction with special vibration rolls. Fig. 5,shows on a larger scale a contrivance for causing a roll to vibrate. Fig. 6 shows on a larger scale a contrivance for causing the shell of a roll to vibrate. The wire is indicated by I, the apron by 2 and the deckels by 3. 4 indicates a member between the apron and the wire in the shape of a band which is stretched between the springs 5 and caused to vibrate violently by means of the alternating current vibrator 6.

The slices which are usually found on Fourdrinier machines are indicated by l. The tablerolls supporting the wire are indicated by 8. The

member 4 may be of some other form than that present invention is greatly enhanced if the apron is made of metal or some alloy,

effect as possible, the slices 1 may also with or without an irregular surface.

Fig. 3 shows a form of construction of the invention in which a vibrating breast-roll is used, if wanted also with vibrating tableerolls. In this case, the fiber-suspension is conveyed from the stuff-box l0 over the apron .2 to the wire I. The vibrations are here transmitted from the breastroll 9, which may suitably be provided with a rubber jacket, to the wire I. The table-rolls may also be kept in a state of vibration, in which case they also should be covered with rubber. The vibrations should be greatest where the apron 2 ends and the pulp is thus transferred to the wire. The distance from the end of the apron to the'breast-roll should thus be as small as possible. In order to produce as great an be caused to vibrate.

Fig. 4 shows" another form of execution in which the fiber-suspension is transferred to the wire I from a flow box I I through its mouthpiece l2 which may be caused to vibrate. The vibrations are in this case transmitted to the wire by means of rolls [3 and Ill on either side of the wire, which rolls are caused to vibrate rapidly and should be covered with rubber. The table rolls 8 may also be caused to vibrate, in which case they also should be covered with rubber. The distance between the end of themouthpiece l2 and the rolls I3 and I4 should be as short as possible. If the breast-roll does not vibrate, the distance between it and the rolls l3 and [4 should be as large as possible. ,There is, however, no reason why the breast-roll 0 should'not vibrate also, in which case the distance between it and the rolls l3 and II may be smaller.

Fig. 5 shows on a larger scale an example of a device by means of which a roll may be caused to vibrate. We will assume that the roll is the roll M in Fig. 4. Its axle-journals ii are supported by the bearings It so that they can move to and fro and the ends of the journals are in contact with the springs l1. These springs are connected by a bar IS with an alternating-current vibrator, which is shown schematically and indicated'by IS. The spring devices should be of such a size that the number of oscillations of the roll itself is in resonance with the number of oscillations of the vibrator. In the case of large rolls, the pressure between the springs and the rotating journals should be transmitted by means of suitable axial-bearings (not shown). It is naturally possible to have two or more rolls operated by the same vibrator.

Fig. 6 shows a form of construction in which only the shell 20 of the roll is'caused to vibrate while its core 2| neither vibrates nor rotates. By means of supports 22, the shell 20, which may be covered with rubber, rests on the core 2|, said supports 22 sliding on the core 2| when the shell rotates.

' there are blocks 24 which -up to On one of the axle-journals l5 of the core there is an axial-bearing 23 in the groove of which are supported by the spring-devices 25. The blocks 24 are connected by means of the member 26 with the alternating- 7 current vibrator l9.

Instead of the supports 22 sliding on the core, supporting members with roller-friction may be used, in which case the core should also rotate. The shell may also be supported by springs which are attached to the core, by which means both sliding and rolling friction may be avoided. It is not necessary to place the vibrator l9 outside the roll, but it may also be placed within the same, which is a very simple matter if an alternating current vibrator is used.

Obviously, vibrations may be transmitted to the flowing stuff on the wire in other ways than those mentioned above, for example, by means of the apron itself or by the slices 1 which are in contact with the upper layer of pulp or by means of one or several wires or bands-or groups of wires or bands -placed in or close to the flowing stuff on the wire or by means of combinations of these devices. In each of these cases, the vibrating members, i. e., the apron, slices, bands, wires etc. are made either with smooth surfaces or with agitators or grooves or other irregularities suitable for producing violent agitation. The main thing is, however, that the vibrations of the member or members which produce the agitation are of high frequency, for example, as has been mentioned, with at least about l000-6000 oscillations per minute.

When using a vibrating apron or the band marked 4 in Fig. 1, it often proves advisable to have the apron or the band comparatively wide, about 1 metre or, in some cases, still wider. Since the stream of pulp is, as one might say, caused to flow over a vibrating bottom, so-called laminary fiow is hindered or prevented and, in consequence, the pointing of the fibers in parallel directions which is a result of such a flow.

Corresponding advantages are attained by the vibration of the mouthpiece of the flow box, when such a box is used.

When a vibrating brations may be transmitted from the vibrator or vibrators to the wire by the breast roll, by the table rolls or by special rolls on each side of the wire, preferably covered with'rubber, which hold the wire between themselves by means of a suitable pressure or, finally, by means of combinations of these devices.

Instead of alternating-current vibrators any other electrical or mechanical vibrators may be used which are adapted to create vibrations of veryhigh frequency, at least 1.000 per minute. In practice it is suitable to use still higher frequencies, say 4.000, 5.000, 6.000 or more vibrations per minute.

We claim:

1. Improvements in paper or board making -machines for effecting an improved felting ofthe wire-cloth is used, the vithe apron, and alternating-current vibrators adapted to impart to said breast-roll, apron and wire cloth high frequency vibrations, at least 5 eomooi 7 i000 perminute, and in which theroiis are prowire cloth, the saw mils being provided with a vided with a fixed case and e, 'oietebie shell. fixed core and a. mtatabie shell, and alternating- 2.. Improvements in paper or board mamng current vibrators connected with said shell and machines for effecting an improved felting oi adaptefl to impart to the same high frequency the fibers in the pulp, comprising in 'combinevibrations, at least 1000 per minute. tion an endless wire cloth, breast rolls end table rolls for supporting the same, means for imparting longitudinal motion to said wire cloth, a stuff box, en apron-between the stufi box mid the w no mm Emmi.

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